For fetching the fantastic composite screengrabs from /u/iamonlyoneman on /r/killlakill

fetch-kill-la-kill.ps1

$user = 'iamonlyoneman'
$subreddit = 'KillLaKill'
$stateFile = 'fetch-last.txt'

function Get-Page {
  [CmdletBinding()]
  param (
      [Parameter(Mandatory)]
      [string] $Uri,
      [Parameter()]
      [string] $After,
      [Parameter()]
      [string] $Before
  )
  if (![String]::IsNullOrEmpty($Before)) {
    $Uri += "?before=$Before"
  }
  if (![String]::IsNullOrEmpty($After)) {
    if ([String]::IsNullOrEmpty($Before)) {
      $Uri += "?"
    } else {
      $Uri += "&"
    }
    $Uri += "after=$After"
  }
  Invoke-RestMethod -Method Get -Uri $Uri
}
$lastFetched = $null
if (Test-Path -Path $stateFile -PathType Leaf) {
  $lastFetched = Get-Content -Path $stateFile
}
$skipped = @()
$posts = @()
$page = @{data = @{after = $null}}
$done = $false;

Write-Host "Fetching posts from $user in $subreddit"
do {
  $page = Get-Page -Uri "https://www.reddit.com/user/$user/submitted.json" -After $page.data.after
  $posts += $page.data.children | Where-Object {
    if ($done) {
      $false
    } else {
      $done = $_.data.name -eq $lastFetched
      !$done -and $_.data.subreddit -eq $subreddit
    }
  }
  Write-Host '.' -NoNewline
} while ($page.data.after -and !$done)

Write-Host "`n$($posts.count) posts found"

for ($i = $posts.count - 1; $i -ge 0; $i -= 1) {
  Write-Progress -Activity "Downloading Images" -Status "$($posts.count - $i) / $($posts.count)" -PercentComplete (($posts.count - $i) / $posts.count * 100)
  $extension = (Split-Path -Path $posts[$i].data.url -leaf).split('.')[1].ToLower()
  $filename = ("$($posts[$i].data.title)_$($posts[$i].data.name).$extension" -replace "[$([RegEx]::Escape([string][IO.Path]::GetInvalidFileNameChars()))]+","_")
  $escapedFileName = ([Management.Automation.WildcardPattern]::Escape($filename))
  if ($extension -in 'jpeg','jpg','png') {
    Invoke-WebRequest -Uri $posts[$i].data.url -OutFile $escapedFileName
    Rename-Item -LiteralPath $escapedFileName $filename
  } else {
    $skipped += $posts[$i]
  }
  Set-Content -Path $stateFile -Force -Value $posts[$i].data.name
}
Write-Progress -Activity "Downloading Images" -Status "$($posts.count) / $($posts.count)" -Completed
$skipped.data | Select-Object -Property 'name','title','url'